Dispensers of fluid or liquid are commonly used in industrial, business, residential and hospital settings. The most common type of fluid dispensers have plunger pumps with the soap container at the bottom wherein a user pushes a lever or handle downward to draw fluid upward for ejection at a nozzle near the top. Disadvantageously, this type of dispenser requires the user to push the lever or pump handle numerous time upon initial use to draw sufficient fluid upward for dispensing at the nozzle. When this type of dispenser has not been used for a period of time, fluid in the pump sometimes flows back to the soap container due to gravity and again requires numerous pumping before fluid is dispensed.
Since fluid dispensers are often used to dispense cleansing or disinfecting fluids such as soap and anti-microbial gel, it is preferable that the fluid dispensers dispense the fluid without the user contacting the dispensers. Some prior art dispensers have incorporated infrared sensors such that upon detection of a user's hand near the sensors, a predetermined amount of fluid is dispensed. Prior art automatic dispensers are usually wall-mounted or sink-mounted and are powered via electrical outlets. Disadvantageously, these type of mounted automatic dispensers are expensive and not portable. Further, a malfunctioned mounted automatic dispenser requires either a technician for on-site servicing or a technician for often complicated disassembling of the dispensers for off-site servicing.
U.S. patent application Publication No. 2004/0050875 discloses a liquid dispenser that is battery powered and portable. This dispenser also provides a sensor for automatic dispensing of liquid. This dispenser utilizes a rotating helical screw pump to draw fluids from a liquid container at the bottom upward for ejection at a nozzle near the top. Similar to the plunger pump dispensers, disadvantageously, liquid is dispensed with a time delay since it requires numerous rotation of the helical pump to draw sufficient fluid upwards for dispensing at the nozzle. Further, liquid in the helical screw pump is more prone to flow back to the liquid container than the plunger pump, thereby resulting in time delay in dispensing liquid each time the dispenser is used. Another disadvantage is that this prior art liquid dispenser cannot be used to dispense fluid with high viscosity, such as gel, because the rotation of the helical screw pump against the gel along the helical pump causes the viscosity characteristic to break down and liquefies the gel.
Therefore, there is a need for a fluid dispenser that automatically and promptly dispenses fluid of various viscosity, be self-contained and portable.